net/mac80211/wpa.c

   1 /*
   2  * Copyright 2002-2004, Instant802 Networks, Inc.
   3  * Copyright 2008, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  */
   9
  10 #include <linux/netdevice.h>
  11 #include <linux/types.h>
  12 #include <linux/slab.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/compiler.h>
  15 #include <linux/ieee80211.h>
  16 #include <asm/unaligned.h>
  17 #include <net/mac80211.h>
  18
  19 #include "ieee80211_i.h"
  20 #include "michael.h"
  21 #include "tkip.h"
  22 #include "aes_ccm.h"
  23 #include "aes_cmac.h"
  24 #include "wpa.h"
  25
  26 ieee80211_tx_result
  27 ieee80211_tx_h_michael_mic_add(struct ieee80211_tx_data *tx)
  28 {
  29         u8 *data, *key, *mic, key_offset;
  30         size_t data_len;
  31         unsigned int hdrlen;
  32         struct ieee80211_hdr *hdr;
  33         struct sk_buff *skb = tx->skb;
  34         int authenticator;
  35         int wpa_test = 0;
  36         int tail;
  37
  38         hdr = (struct ieee80211_hdr *)skb->data;
  39         if (!tx->key || tx->key->conf.alg != ALG_TKIP || skb->len < 24 ||
  40             !ieee80211_is_data_present(hdr->frame_control))
  41                 return TX_CONTINUE;
  42
  43         hdrlen = ieee80211_hdrlen(hdr->frame_control);
  44         if (skb->len < hdrlen)
  45                 return TX_DROP;
  46
  47         data = skb->data + hdrlen;
  48         data_len = skb->len - hdrlen;
  49
  50         if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
  51             !(tx->flags & IEEE80211_TX_FRAGMENTED) &&
  52             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_MMIC) &&
  53             !wpa_test) {
  54                 /* hwaccel - with no need for preallocated room for MMIC */
  55                 return TX_CONTINUE;
  56         }
  57
  58         tail = MICHAEL_MIC_LEN;
  59         if (!(tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE))
  60                 tail += TKIP_ICV_LEN;
  61
  62         if (WARN_ON(skb_tailroom(skb) < tail ||
  63                     skb_headroom(skb) < TKIP_IV_LEN))
  64                 return TX_DROP;
  65
  66 #if 0
  67         authenticator = fc & IEEE80211_FCTL_FROMDS; /* FIX */
  68 #else
  69         authenticator = 1;
  70 #endif
  71         key_offset = authenticator ?
  72                 NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY :
  73                 NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY;
  74         key = &tx->key->conf.key[key_offset];
  75         mic = skb_put(skb, MICHAEL_MIC_LEN);
  76         michael_mic(key, hdr, data, data_len, mic);
  77
  78         return TX_CONTINUE;
  79 }
  80
  81
  82 ieee80211_rx_result
  83 ieee80211_rx_h_michael_mic_verify(struct ieee80211_rx_data *rx)
  84 {
  85         u8 *data, *key = NULL, key_offset;
  86         size_t data_len;
  87         unsigned int hdrlen;
  88         struct ieee80211_hdr *hdr;
  89         u8 mic[MICHAEL_MIC_LEN];
  90         struct sk_buff *skb = rx->skb;
  91         int authenticator = 1, wpa_test = 0;
  92
  93         /* No way to verify the MIC if the hardware stripped it */
  94         if (rx->status->flag & RX_FLAG_MMIC_STRIPPED)
  95                 return RX_CONTINUE;
  96
  97         hdr = (struct ieee80211_hdr *)skb->data;
  98         if (!rx->key || rx->key->conf.alg != ALG_TKIP ||
  99             !ieee80211_has_protected(hdr->frame_control) ||
 100             !ieee80211_is_data_present(hdr->frame_control))
 101                 return RX_CONTINUE;
 102
 103         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 104         if (skb->len < hdrlen + MICHAEL_MIC_LEN)
 105                 return RX_DROP_UNUSABLE;
 106
 107         data = skb->data + hdrlen;
 108         data_len = skb->len - hdrlen - MICHAEL_MIC_LEN;
 109
 110 #if 0
 111         authenticator = fc & IEEE80211_FCTL_TODS; /* FIX */
 112 #else
 113         authenticator = 1;
 114 #endif
 115         key_offset = authenticator ?
 116                 NL80211_TKIP_DATA_OFFSET_RX_MIC_KEY :
 117                 NL80211_TKIP_DATA_OFFSET_TX_MIC_KEY;
 118         key = &rx->key->conf.key[key_offset];
 119         michael_mic(key, hdr, data, data_len, mic);
 120         if (memcmp(mic, data + data_len, MICHAEL_MIC_LEN) != 0 || wpa_test) {
 121                 if (!(rx->flags & IEEE80211_RX_RA_MATCH))
 122                         return RX_DROP_UNUSABLE;
 123
 124                 mac80211_ev_michael_mic_failure(rx->sdata, rx->key->conf.keyidx,
 125                                                 (void *) skb->data);
 126                 return RX_DROP_UNUSABLE;
 127         }
 128
 129         /* remove Michael MIC from payload */
 130         skb_trim(skb, skb->len - MICHAEL_MIC_LEN);
 131
 132         /* update IV in key information to be able to detect replays */
 133         rx->key->u.tkip.rx[rx->queue].iv32 = rx->tkip_iv32;
 134         rx->key->u.tkip.rx[rx->queue].iv16 = rx->tkip_iv16;
 135
 136         return RX_CONTINUE;
 137 }
 138
 139
 140 static int tkip_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 141 {
 142         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 143         struct ieee80211_key *key = tx->key;
 144         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 145         unsigned int hdrlen;
 146         int len, tail;
 147         u8 *pos;
 148
 149         if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
 150             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV)) {
 151                 /* hwaccel - with no need for preallocated room for IV/ICV */
 152                 info->control.hw_key = &tx->key->conf;
 153                 return 0;
 154         }
 155
 156         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 157         len = skb->len - hdrlen;
 158
 159         if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
 160                 tail = 0;
 161         else
 162                 tail = TKIP_ICV_LEN;
 163
 164         if (WARN_ON(skb_tailroom(skb) < tail ||
 165                     skb_headroom(skb) < TKIP_IV_LEN))
 166                 return -1;
 167
 168         pos = skb_push(skb, TKIP_IV_LEN);
 169         memmove(pos, pos + TKIP_IV_LEN, hdrlen);
 170         pos += hdrlen;
 171
 172         /* Increase IV for the frame */
 173         key->u.tkip.tx.iv16++;
 174         if (key->u.tkip.tx.iv16 == 0)
 175                 key->u.tkip.tx.iv32++;
 176
 177         if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
 178                 /* hwaccel - with preallocated room for IV */
 179                 ieee80211_tkip_add_iv(pos, key, key->u.tkip.tx.iv16);
 180
 181                 info->control.hw_key = &tx->key->conf;
 182                 return 0;
 183         }
 184
 185         /* Add room for ICV */
 186         skb_put(skb, TKIP_ICV_LEN);
 187
 188         hdr = (struct ieee80211_hdr *) skb->data;
 189         ieee80211_tkip_encrypt_data(tx->local->wep_tx_tfm,
 190                                     key, pos, len, hdr->addr2);
 191         return 0;
 192 }
 193
 194
 195 ieee80211_tx_result
 196 ieee80211_crypto_tkip_encrypt(struct ieee80211_tx_data *tx)
 197 {
 198         struct sk_buff *skb = tx->skb;
 199         int i;
 200
 201         ieee80211_tx_set_protected(tx);
 202
 203         if (tkip_encrypt_skb(tx, skb) < 0)
 204                 return TX_DROP;
 205
 206         if (tx->extra_frag) {
 207                 for (i = 0; i < tx->num_extra_frag; i++) {
 208                         if (tkip_encrypt_skb(tx, tx->extra_frag[i]))
 209                                 return TX_DROP;
 210                 }
 211         }
 212
 213         return TX_CONTINUE;
 214 }
 215
 216
 217 ieee80211_rx_result
 218 ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
 219 {
 220         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) rx->skb->data;
 221         int hdrlen, res, hwaccel = 0, wpa_test = 0;
 222         struct ieee80211_key *key = rx->key;
 223         struct sk_buff *skb = rx->skb;
 224
 225         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 226
 227         if (!ieee80211_is_data(hdr->frame_control))
 228                 return RX_CONTINUE;
 229
 230         if (!rx->sta || skb->len - hdrlen < 12)
 231                 return RX_DROP_UNUSABLE;
 232
 233         if (rx->status->flag & RX_FLAG_DECRYPTED) {
 234                 if (rx->status->flag & RX_FLAG_IV_STRIPPED) {
 235                         /*
 236                          * Hardware took care of all processing, including
 237                          * replay protection, and stripped the ICV/IV so
 238                          * we cannot do any checks here.
 239                          */
 240                         return RX_CONTINUE;
 241                 }
 242
 243                 /* let TKIP code verify IV, but skip decryption */
 244                 hwaccel = 1;
 245         }
 246
 247         res = ieee80211_tkip_decrypt_data(rx->local->wep_rx_tfm,
 248                                           key, skb->data + hdrlen,
 249                                           skb->len - hdrlen, rx->sta->sta.addr,
 250                                           hdr->addr1, hwaccel, rx->queue,
 251                                           &rx->tkip_iv32,
 252                                           &rx->tkip_iv16);
 253         if (res != TKIP_DECRYPT_OK || wpa_test)
 254                 return RX_DROP_UNUSABLE;
 255
 256         /* Trim ICV */
 257         skb_trim(skb, skb->len - TKIP_ICV_LEN);
 258
 259         /* Remove IV */
 260         memmove(skb->data + TKIP_IV_LEN, skb->data, hdrlen);
 261         skb_pull(skb, TKIP_IV_LEN);
 262
 263         return RX_CONTINUE;
 264 }
 265
 266
 267 static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 268                                 int encrypted)
 269 {
 270         __le16 mask_fc;
 271         int a4_included, mgmt;
 272         u8 qos_tid;
 273         u8 *b_0, *aad;
 274         u16 data_len, len_a;
 275         unsigned int hdrlen;
 276         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 277
 278         b_0 = scratch + 3 * AES_BLOCK_LEN;
 279         aad = scratch + 4 * AES_BLOCK_LEN;
 280
 281         /*
 282          * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
 283          * Retry, PwrMgt, MoreData; set Protected
 284          */
 285         mgmt = ieee80211_is_mgmt(hdr->frame_control);
 286         mask_fc = hdr->frame_control;
 287         mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
 288                                 IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
 289         if (!mgmt)
 290                 mask_fc &= ~cpu_to_le16(0x0070);
 291         mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 292
 293         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 294         len_a = hdrlen - 2;
 295         a4_included = ieee80211_has_a4(hdr->frame_control);
 296
 297         if (ieee80211_is_data_qos(hdr->frame_control))
 298                 qos_tid = *ieee80211_get_qos_ctl(hdr) & IEEE80211_QOS_CTL_TID_MASK;
 299         else
 300                 qos_tid = 0;
 301
 302         data_len = skb->len - hdrlen - CCMP_HDR_LEN;
 303         if (encrypted)
 304                 data_len -= CCMP_MIC_LEN;
 305
 306         /* First block, b_0 */
 307         b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
 308         /* Nonce: Nonce Flags | A2 | PN
 309          * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
 310          */
 311         b_0[1] = qos_tid | (mgmt << 4);
 312         memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
 313         memcpy(&b_0[8], pn, CCMP_PN_LEN);
 314         /* l(m) */
 315         put_unaligned_be16(data_len, &b_0[14]);
 316
 317         /* AAD (extra authenticate-only data) / masked 802.11 header
 318          * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
 319         put_unaligned_be16(len_a, &aad[0]);
 320         put_unaligned(mask_fc, (__le16 *)&aad[2]);
 321         memcpy(&aad[4], &hdr->addr1, 3 * ETH_ALEN);
 322
 323         /* Mask Seq#, leave Frag# */
 324         aad[22] = *((u8 *) &hdr->seq_ctrl) & 0x0f;
 325         aad[23] = 0;
 326
 327         if (a4_included) {
 328                 memcpy(&aad[24], hdr->addr4, ETH_ALEN);
 329                 aad[30] = qos_tid;
 330                 aad[31] = 0;
 331         } else {
 332                 memset(&aad[24], 0, ETH_ALEN + IEEE80211_QOS_CTL_LEN);
 333                 aad[24] = qos_tid;
 334         }
 335 }
 336
 337
 338 static inline void ccmp_pn2hdr(u8 *hdr, u8 *pn, int key_id)
 339 {
 340         hdr[0] = pn[5];
 341         hdr[1] = pn[4];
 342         hdr[2] = 0;
 343         hdr[3] = 0x20 | (key_id << 6);
 344         hdr[4] = pn[3];
 345         hdr[5] = pn[2];
 346         hdr[6] = pn[1];
 347         hdr[7] = pn[0];
 348 }
 349
 350
 351 static inline void ccmp_hdr2pn(u8 *pn, u8 *hdr)
 352 {
 353         pn[0] = hdr[7];
 354         pn[1] = hdr[6];
 355         pn[2] = hdr[5];
 356         pn[3] = hdr[4];
 357         pn[4] = hdr[1];
 358         pn[5] = hdr[0];
 359 }
 360
 361
 362 static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 363 {
 364         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 365         struct ieee80211_key *key = tx->key;
 366         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 367         int hdrlen, len, tail;
 368         u8 *pos, *pn;
 369         int i;
 370         bool skip_hw;
 371
 372         skip_hw = (tx->key->conf.flags & IEEE80211_KEY_FLAG_SW_MGMT) &&
 373                 ieee80211_is_mgmt(hdr->frame_control);
 374
 375         if ((tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) &&
 376             !(tx->key->conf.flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
 377             !skip_hw) {
 378                 /* hwaccel - with no need for preallocated room for CCMP
 379                  * header or MIC fields */
 380                 info->control.hw_key = &tx->key->conf;
 381                 return 0;
 382         }
 383
 384         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 385         len = skb->len - hdrlen;
 386
 387         if (key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE)
 388                 tail = 0;
 389         else
 390                 tail = CCMP_MIC_LEN;
 391
 392         if (WARN_ON(skb_tailroom(skb) < tail ||
 393                     skb_headroom(skb) < CCMP_HDR_LEN))
 394                 return -1;
 395
 396         pos = skb_push(skb, CCMP_HDR_LEN);
 397         memmove(pos, pos + CCMP_HDR_LEN, hdrlen);
 398         hdr = (struct ieee80211_hdr *) pos;
 399         pos += hdrlen;
 400
 401         /* PN = PN + 1 */
 402         pn = key->u.ccmp.tx_pn;
 403
 404         for (i = CCMP_PN_LEN - 1; i >= 0; i--) {
 405                 pn[i]++;
 406                 if (pn[i])
 407                         break;
 408         }
 409
 410         ccmp_pn2hdr(pos, pn, key->conf.keyidx);
 411
 412         if ((key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) && !skip_hw) {
 413                 /* hwaccel - with preallocated room for CCMP header */
 414                 info->control.hw_key = &tx->key->conf;
 415                 return 0;
 416         }
 417
 418         pos += CCMP_HDR_LEN;
 419         ccmp_special_blocks(skb, pn, key->u.ccmp.tx_crypto_buf, 0);
 420         ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, key->u.ccmp.tx_crypto_buf, pos, len,
 421                                   pos, skb_put(skb, CCMP_MIC_LEN));
 422
 423         return 0;
 424 }
 425
 426
 427 ieee80211_tx_result
 428 ieee80211_crypto_ccmp_encrypt(struct ieee80211_tx_data *tx)
 429 {
 430         struct sk_buff *skb = tx->skb;
 431         int i;
 432
 433         ieee80211_tx_set_protected(tx);
 434
 435         if (ccmp_encrypt_skb(tx, skb) < 0)
 436                 return TX_DROP;
 437
 438         if (tx->extra_frag) {
 439                 for (i = 0; i < tx->num_extra_frag; i++) {
 440                         if (ccmp_encrypt_skb(tx, tx->extra_frag[i]))
 441                                 return TX_DROP;
 442                 }
 443         }
 444
 445         return TX_CONTINUE;
 446 }
 447
 448
 449 ieee80211_rx_result
 450 ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
 451 {
 452         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)rx->skb->data;
 453         int hdrlen;
 454         struct ieee80211_key *key = rx->key;
 455         struct sk_buff *skb = rx->skb;
 456         u8 pn[CCMP_PN_LEN];
 457         int data_len;
 458
 459         hdrlen = ieee80211_hdrlen(hdr->frame_control);
 460
 461         if (!ieee80211_is_data(hdr->frame_control) &&
 462             !ieee80211_is_robust_mgmt_frame(hdr))
 463                 return RX_CONTINUE;
 464
 465         data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;
 466         if (!rx->sta || data_len < 0)
 467                 return RX_DROP_UNUSABLE;
 468
 469         if ((rx->status->flag & RX_FLAG_DECRYPTED) &&
 470             (rx->status->flag & RX_FLAG_IV_STRIPPED))
 471                 return RX_CONTINUE;
 472
 473         ccmp_hdr2pn(pn, skb->data + hdrlen);
 474
 475         if (memcmp(pn, key->u.ccmp.rx_pn[rx->queue], CCMP_PN_LEN) <= 0) {
 476                 key->u.ccmp.replays++;
 477                 return RX_DROP_UNUSABLE;
 478         }
 479
 480         if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
 481                 /* hardware didn't decrypt/verify MIC */
 482                 ccmp_special_blocks(skb, pn, key->u.ccmp.rx_crypto_buf, 1);
 483
 484                 if (ieee80211_aes_ccm_decrypt(
 485                             key->u.ccmp.tfm, key->u.ccmp.rx_crypto_buf,
 486                             skb->data + hdrlen + CCMP_HDR_LEN, data_len,
 487                             skb->data + skb->len - CCMP_MIC_LEN,
 488                             skb->data + hdrlen + CCMP_HDR_LEN))
 489                         return RX_DROP_UNUSABLE;
 490         }
 491
 492         memcpy(key->u.ccmp.rx_pn[rx->queue], pn, CCMP_PN_LEN);
 493
 494         /* Remove CCMP header and MIC */
 495         skb_trim(skb, skb->len - CCMP_MIC_LEN);
 496         memmove(skb->data + CCMP_HDR_LEN, skb->data, hdrlen);
 497         skb_pull(skb, CCMP_HDR_LEN);
 498
 499         return RX_CONTINUE;
 500 }
 501
 502
 503 static void bip_aad(struct sk_buff *skb, u8 *aad)
 504 {
 505         /* BIP AAD: FC(masked) || A1 || A2 || A3 */
 506
 507         /* FC type/subtype */
 508         aad[0] = skb->data[0];
 509         /* Mask FC Retry, PwrMgt, MoreData flags to zero */
 510         aad[1] = skb->data[1] & ~(BIT(4) | BIT(5) | BIT(6));
 511         /* A1 || A2 || A3 */
 512         memcpy(aad + 2, skb->data + 4, 3 * ETH_ALEN);
 513 }
 514
 515
 516 static inline void bip_ipn_swap(u8 *d, const u8 *s)
 517 {
 518         *d++ = s[5];
 519         *d++ = s[4];
 520         *d++ = s[3];
 521         *d++ = s[2];
 522         *d++ = s[1];
 523         *d = s[0];
 524 }
 525
 526
 527 ieee80211_tx_result
 528 ieee80211_crypto_aes_cmac_encrypt(struct ieee80211_tx_data *tx)
 529 {
 530         struct sk_buff *skb = tx->skb;
 531         struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 532         struct ieee80211_key *key = tx->key;
 533         struct ieee80211_mmie *mmie;
 534         u8 *pn, aad[20];
 535         int i;
 536
 537         if (tx->key->flags & KEY_FLAG_UPLOADED_TO_HARDWARE) {
 538                 /* hwaccel */
 539                 info->control.hw_key = &tx->key->conf;
 540                 return 0;
 541         }
 542
 543         if (WARN_ON(skb_tailroom(skb) < sizeof(*mmie)))
 544                 return TX_DROP;
 545
 546         mmie = (struct ieee80211_mmie *) skb_put(skb, sizeof(*mmie));
 547         mmie->element_id = WLAN_EID_MMIE;
 548         mmie->length = sizeof(*mmie) - 2;
 549         mmie->key_id = cpu_to_le16(key->conf.keyidx);
 550
 551         /* PN = PN + 1 */
 552         pn = key->u.aes_cmac.tx_pn;
 553
 554         for (i = sizeof(key->u.aes_cmac.tx_pn) - 1; i >= 0; i--) {
 555                 pn[i]++;
 556                 if (pn[i])
 557                         break;
 558         }
 559         bip_ipn_swap(mmie->sequence_number, pn);
 560
 561         bip_aad(skb, aad);
 562
 563         /*
 564          * MIC = AES-128-CMAC(IGTK, AAD || Management Frame Body || MMIE, 64)
 565          */
 566         ieee80211_aes_cmac(key->u.aes_cmac.tfm, key->u.aes_cmac.tx_crypto_buf,
 567                            aad, skb->data + 24, skb->len - 24, mmie->mic);
 568
 569         return TX_CONTINUE;
 570 }
 571
 572
 573 ieee80211_rx_result
 574 ieee80211_crypto_aes_cmac_decrypt(struct ieee80211_rx_data *rx)
 575 {
 576         struct sk_buff *skb = rx->skb;
 577         struct ieee80211_key *key = rx->key;
 578         struct ieee80211_mmie *mmie;
 579         u8 aad[20], mic[8], ipn[6];
 580         struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
 581
 582         if (!ieee80211_is_mgmt(hdr->frame_control))
 583                 return RX_CONTINUE;
 584
 585         if ((rx->status->flag & RX_FLAG_DECRYPTED) &&
 586             (rx->status->flag & RX_FLAG_IV_STRIPPED))
 587                 return RX_CONTINUE;
 588
 589         if (skb->len < 24 + sizeof(*mmie))
 590                 return RX_DROP_UNUSABLE;
 591
 592         mmie = (struct ieee80211_mmie *)
 593                 (skb->data + skb->len - sizeof(*mmie));
 594         if (mmie->element_id != WLAN_EID_MMIE ||
 595             mmie->length != sizeof(*mmie) - 2)
 596                 return RX_DROP_UNUSABLE; /* Invalid MMIE */
 597
 598         bip_ipn_swap(ipn, mmie->sequence_number);
 599
 600         if (memcmp(ipn, key->u.aes_cmac.rx_pn, 6) <= 0) {
 601                 key->u.aes_cmac.replays++;
 602                 return RX_DROP_UNUSABLE;
 603         }
 604
 605         if (!(rx->status->flag & RX_FLAG_DECRYPTED)) {
 606                 /* hardware didn't decrypt/verify MIC */
 607                 bip_aad(skb, aad);
 608                 ieee80211_aes_cmac(key->u.aes_cmac.tfm,
 609                                    key->u.aes_cmac.rx_crypto_buf, aad,
 610                                    skb->data + 24, skb->len - 24, mic);
 611                 if (memcmp(mic, mmie->mic, sizeof(mmie->mic)) != 0) {
 612                         key->u.aes_cmac.icverrors++;
 613                         return RX_DROP_UNUSABLE;
 614                 }
 615         }
 616
 617         memcpy(key->u.aes_cmac.rx_pn, ipn, 6);
 618
 619         /* Remove MMIE */
 620         skb_trim(skb, skb->len - sizeof(*mmie));
 621
 622         return RX_CONTINUE;
 623 }